Grinding disc



June 12, 1956 Filed Aug. 31, 1953 F. REIDENBACH GRINDING DISC 2 Sheets-Sheet 1 June 1956 F. REIDENBACH 2,749,681

GRINDING DISC Filed Aug. 31, 1955 2 Sheets-Sheet 2 M r I i 60 United States Patent GRINDING DISC Fritz' Reidenbach, Wennigsen on the Deister, Germany, assignor to A. Stephen u. Sohne, Hamelu at the Weser, Germany Application August 31, 1953, Serial No. 377,548

Claims priority, application Sweden December 31, 1952 8 Claims. (Cl. 51-195) This invention relates to a grinding disk with inspection apertures for controlling the grinding operation of its flat surface remote from the eye. It consists for example of a thin plate with a coating of abrasive material on one or both sides and its surface is bevelled at the edges of the inspection apertures.

The grinding disk combines a number of important advantages. In the first place it makes it possible to observe through the disk the tool, its behaviour and the progressive grinding eifect during the entire grinding operations so that it is no longer necessary to remove and replace repeatedly the tool from and onto the grinding disk with the result that the disadvantages which inevitably result therefrom are avoided. Moreover, it can be made in the simplest, cheapest and most compact form imaginable, so that even the smallest works can purchase and use it. Furthermore, it stands rough usage in grinding shops as the take-up edges formed by the inspection apertures are protected against breaking away if they are of shaped stone, and do not tear or peel ofi if an abrasive carrier, such as abrasive cloth, is stuck on the disk.

In addition, the disks can be piled up in large numbers, kept in store and transported without any difiiculty, and finally they also present the advantage that the two flat surfaces can be coated with abrasive of different grain coarseness and it is possible to change over to the grain actually required by a few manipulations.

It is particularly advantageous for the grinding surfaces of the disk according to the invention to be of dark colour, preferably black, either the abrasive or its backing are of suitable colour from the outset or these are subsequently coloured. By this means a contrast is obtained between the grinding surface and the tool which becomes visible through the inspection apertures during the grinding operation, which contrast gives a clear picture.

In one form of construction of the disk according to the invention, which is suitable for certain purposes, separate inspection apertures, for example of circular shape, are arranged in one or more spiral lines so that in their projection on a common radius they form together an uninterrupted radially directed window.

Such a construction also presents the advantage of a view thru the entire disk on the one hand and on the other hand it avoids a pronounced weakening of the disk along one or more radii.

Radially directed windows can also be attained, for example by arranging sectors, fingers or the like coated with abrasive material, at distances apart on a rotary carrier, but such elements can also be combined in groups in which they lie mutually parallel.

The invention is illustrated by way of example in the accompanying drawing, in which Fig. 1 shows in perspective a grinding disk of a preferred formation,

Figs. 1a and 1b similar disks of slightly modified form,

Fig. 10 a perspective of another modification,

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Fig. 2 an edge view of a grinding disk with layers partly separated,

Fig. 2a a similar disk of a modified form and Fig. 3, a section on an enlarged scale.

Grinding disks are known for example in U. S. patent to Geoifrion 2,231,900, with axially arranged sight openings or peep holes, which serve for control of the grinding operations through observation by means of an eye viewing the progress of the grinding along the axis of the grinding disk, as in the Geoffrion patent. By the use of such apparatus it is possible to observe the work, its position and the progress of the grinding operation throughout the entire process of such operation as seen through the grinding disk, so that the repeated removal of the disk from the work and its replacement against the same may be done away with. The customary operations of forming suitable disks or like shapes, e. g. thin disks of grinding material into desired shape, hardening them, etc., may now be eliminated, and the accompanying disadvantages are also eliminated.

On the one hand the disks or other molded shapes must possess the necessary strength to hold their shape, and that in spite of pressure against the work being ground, and they must have strength to resist the centrifugal forces engendered in the manufacture and use of such disks and other shapes, as during their use in grinding operations. But furthermore, their manufacture is very expensive and time-consuming and there is much waste by reason of breakage in manufacture, as well as danger from the broken fragments and potsherds.

By reason of such breakage the observation of the manufacturing processes is dangerous. Finally, grinding disks are known that consist of a thin backing covered at one or both faces with grinding material. But such disks do not permit observation of both faces of such a disk (and particularly not the side remote from the Workman) and thus they do not afford the advantages set forth herein as flowing from applicants invention.

In spite of the knowledge of massive grinding disks with sight openings, and in spite of the known non-transparent covered carrier disks, it was long the opinion of those skilled in the art that it was impossible to use carrier disks with peep holes because they could not be ground properly. This invention is therefore based on the new knowledge that the old opinion was in error and rests on the known advantages of grinding disks, with avoidance of their disadvantages, consequently the following characteristics are found in the product of applicants invention.

1. A grinding disk consists of a thin sheet of sheet steel as foundation.

2. The thin sheet is covered at one or both faces with grinding material.

3. The thin (foundation) sheet is provided with sighting orifices.

4. The margins of the sighting openings are beveled.

It is an essential feature of the invention that beveling about the orifices provides free unobstructed passage for the work over the irregularities in the surface of the disks, so that the margins cannot be damaged and particularly that the grinding material cannot be raised off from the surface of the disk:

By the novel construction of the grinding disk (itself otherwise not novel or unknown) applicant has now obtained a degree of perfection that was heretofore unknown and has made practical the utilization of the improved grinding disk.

An added improvement resides in the fact that a dark color occurs between the layers of a grinding disk so made. Such dark coloration is not merely an arbitrary matter nor is it a mere matter of taste, but on the contrary the coloration occurs between the layers and becomes especially noticeable at the sight openings when illuminated, the difference in coloration appearing strongly at the intermediate layers of uncolored material and vice versa.

A steel disk :1 has inspection apertures which may be of different shapes, several of which are shown in Fig. 1. Thus for example the disc a may have simple radial slots d or incisions e. The latter may be formed by separate sectors, fingers or the like 1, mounted in a common holder, for example on or between retaining or clamping discs. Sectors or fingers g or the slots h located betwen them may also be arranged mutually parallel in groups. Circular inspection apertures i'may also be arranged for example in a spiral line k so that in their projection on a radius m they form together a radial slot.

Fig. 2 is divided into two halves and shows how the disk a may be coated with abrasive material. On the left the abrasive material b is applied directly on to the disk a, whereas on the right the abrasive is on a carrier, for example a cloth backing c which in turn is stuck on the two flat surfaces of the disk a.

As can be seen from Fig. 3, the contour edges 11 of the inspection apertures 0 are bevelled as a protection against mechanical wear and tear.

I claim:

1. Grinding disk with inspection apertures for controlling the grinding progress on the surface remote from the eye, comprising a thin plate of sheet steel coated with abrasive material and having inspection apertures, the contours of which are bevelled.

2. Grinding disk as set forth in claim 1, the abrasive on the two sides of the plate having grains of different coarseness.

3. Grinding disk as set forth in claim 1, the two sides of the plate being of dark colour, preferably black.

4. Grinding disk as set forth in claim 1, the inspection apertures being arranged on spiral lines so that in the projection of these apertures on a common radius several of the apertures together always form an uninterrupted radially directed inspection window.

5. Grinding disk as set forth in claim 1, the plate being composed of fingers coated with abrasive material and arranged in groups mutually parallel at distances apart on a rotary carrier.

6. An abrasive disk comprising a thin supporting plate of steel coated with abrasive material and having sighting apertures extending through said disk said plate being beveled about said apertures.

7. An abrasive disk as in claim 6, wherein the abrasive material is darker in color than the remaining layers of the disk.

8. An abrasive disk comprising a sheet metal plate coated on one or both faces with a relatively dark abrasive material and having sighting apertures extending therethrough with beveled margins.

References Cited in the file of this patent UNITED STATES PATENTS 451,509 MacLean May 5, 1891 2,047,649 Robinson July 14, 1936 2,175,073 Amstutz Oct. 3, 1939 2,231,900 Geoifrion Feb. 18, 1941 2,334,642 Moore Nov. 16, 1943 2,376,254 Humphrey et a1. May 15, 1945 

6. AN ABRASIVE DISK COMPRISING A THIN SUPPORTING PLATE OF STEEL COATED WITH ABRASIVE MATERIAL AND HAVING SIGHTING APERTURES EXTENDING THROUGH SAID DISK SAID PLATE BEING BEVELED ABOUT SAID APERTURES. 